The present invention relates to a method and apparatus for converting organic materials into a usable synthetic gas (syngas) by way of gasification and more particularly to a method and apparatus for converting organic materials into a usable syngas by way of steam reformation with the use of induction generated heat.
Various types of high temperature processes are employed to convert organic materials into syngas or into compounds that are more acceptable for discharge into the environment. Organic materials are any materials that contain carbon which include but are not limited to petrochemical streams, refinery streams, crude oil, natural gas, coal, polymeric wastes, municipal wastes, toxic and hazardous wastes, biomass, medical wastes, and automobile wastes. Non-limiting examples of processes that can be used for such conversion of such organic materials include incineration, combustion, pyrolysis, thermolysis, decomposition, gasification, and steam reformation.
It is known in the art to incinerate certain types of organic materials in order to utilize its energy content for the production of electrical energy; for the generation of heat; to destroy toxic and hazardous organic components; or to reduce drastically the volume of the material to be disposed. Incineration is generally referred to as the exothermic conversion of organic materials by combustion (burning) to ash, carbon dioxide, and water vapor.
Incineration facilities for such organic materials typically require complicated flue or smoke gas purification due to the danger that highly toxic chlorine-containing organic substances, such as, dioxins and furans, may be formed. These highly toxic chlorine-containing organic substances may be formed from chlorine compounds in the organic material feedstock during combustion or in the cooling phase of primary combustion gases. In addition, nitrogen from the atmosphere can combine with oxygen in the incinerator to produce NOx which are pollutants. Furthermore, there is a growing resistance from both the pubic and regulatory agencies toward incineration because of the high volume of gaseous discharge, a part of which may be toxic. Also, incineration inherently involves the use of open flames which can be hazardous at certain locations, such as at petroleum refineries and chemical plants.
Changing regulations, inspired by public concerns aimed at safeguarding the environment, have become the catalyst for the development of advanced technologies designed to minimize the amount of waste by separating waste components and recovering reusable components. These technologies must, at the same time, reduce fugitive discharges below regulatory tolerance levels while maintaining an effective monitoring network.
A number of treatment techniques have been employed to break down the organic materials while decreasing or eliminating certain pollutants discharged to the environment such as NOx, dioxins, and furans. In an effort to address the concerns of incineration, for example, the process of gasification has been developed as a technology solution for solving the inherent problems of incineration. Gasification is generally known as a process wherein organic materials are converted into a syngas in the absence or presence of free oxygen.
In particular, one type of gasification technology that is being developed for solving the inherent problems of incineration is steam reformation. Steam reformation is considered a subcategory of gasification and involves the high temperature chemical breakdown of organic compounds in a low oxygen or oxygen-free environment. The steam reformation process is an endothermic process whereby organic materials in combination with water vapor are converted into a syngas. As an endothermic process, steam reforming thereby requires an energy input to drive the steam reformation reaction.
In an effort to supply heat to drive the steam reformation reaction, various methods of heating have been employed, including gas fired heat, electrical resistance, microwaves, and steam. Most steam reformation processes use gas fired heaters wherein the gas fired heaters create an emission point that may or may not be regulated by the EPA or state environmental agency. Gas fired heaters suffer from several short-comings, such as an undesirable hot environment; a high level of operator skill; relatively poor temperature control; and an open flame. In an effort to address these concerns, a number of alternative heat sources have been employed in which the organic material is heated without use of combustion or open flames. In particular, these techniques employ microwaves or electrical resistance.
An example of heating by electrical resistance is found in U.S. Pat. No. 5,184,950 to Fraysse et al. which discloses a process and device for the decontamination of solid material that employs resistance heating elements to heat a treatment enclosure at a temperature of about 500° C. During treatment, a vacuum is maintained within the enclosure, and a heated inert gas may be pumped into the enclosure, depending upon the type of material to be treated. Unfortunately, electrical resistance heating may be inefficient and costly and may not efficiently heat materials to a high enough temperature to drive either a pyrolysis or steam reformation reaction. On the other hand, induction heating has the potential of providing a more efficient alternative to resistance heating. However, until this invention there was no efficient induction heating techniques employing the combination of pyrolysis and steam reformation of organic materials.
An example of induction heating is found in U.S. Pat. No. 5,710,360 to Self et al. which discloses a thermal desorption system for decontaminating various types of materials. During decontamination, induction heating is employed to heat the thermal desorption chamber so that certain target compounds are volatized and removed from the waste materials. While this thermal desorption system employs induction heating, the system was not designed for the steam reformation of organic materials.
An example of microwave heating is found in U.S. Pat. No. 6,398,921 to Moraski which discloses a gasification reaction driven by a high intensity microwave field. The microwave gasifier enables the endothermic gasification process wherein target organic materials are converted into a usable combustable gas, such as syngas. Unfortunately, it is difficult to create a uniform energy distribution with microwave heating. Also, microwave heating cannot easily be used to heat all materials because not all materials behave the same to the microwave wave length. Therefore, induction heating provides a more efficient alternative to microwave heating because induction heating can provide a uniform heat distribution regardless of the organic material being heated.
Another advantage of inductive heating is the potential for shorter residence times of the steam reformation reaction. Certain methods of inductively heating a steam reformer may create a significantly shorter residence time as compared to the related art. For example, inductively heating a steam reformer can result in a residence time of about ¼ second whereas any of the non-induction heating technology disclosed in the related art may have a higher residence time of about 2 seconds or more.
In view of the foregoing, it is apparent that a need exists in the art for an improved process for decontamination and steam reforming of organic materials.